Solar panels, partial shade options.

[ithet]

I am looking at fitting semi flexible solar onto the hatch garage as I have nowhere else to mount panels. I can get a max 80w panel that just fits the total area available. However, I could alternatively fit two narrow 30w panels side by side lengthwise in the same area. As the boom will give partial shading I want to know if the option of the two lower output panels wired in parallel (or with separate controllers if necessary) will provide a better solution (i.e. higher average output). What is the experts opinion?

 

[LadyInBed]

When the boat is sailing the solar could well be clear, when not sailing, jack up the topping lift to reduce shading?

 

[Mikedefieslife]

The two smaller panels are likely to be worse. Overall smaller panels are tend to be less efficient, and in your case won't amount to the total rated sum of the larger panel.

In addition I imagine that any shade is likely to end up partially covering the two smaller panels anyhow.

 

[macd]

Apart from any technical considerations, ithet, the practical answer would depend on a variety of other factors. What sort of sailing do you do? Are you seeking to charge the batteries when under way, or primarily when berthed? If the latter, what sort of berth?: swinging mooring and, say, a slot on a pontoon are quite different in terms of solar effect.

 

[ithet]

Apart from any technical considerations, ithet, the practical answer would depend on a variety of other factors. What sort of sailing do you do? Are you seeking to charge the batteries when under way, or primarily when berthed? If the latter, what sort of berth?: swinging mooring and, say, a slot on a pontoon are quite different in terms of solar effect.

Good questions. We are on a SW facing mid river pontoon mooring. Currently a small removable panel keeps the batteries topped up when on the mooring. I want replace with a larger fixed panel to help keep the battery levels up when we are cruising if we spend say 24-36 hours away from shore-power. We tend to do long day sails then stay a few days. We are a 10m AWB with the usual comforts - compressor fridge, pressurised water, led lighting, stereo radio etc. I know that 60-80w will not fully keep up with these loads, but want to reduce the battery drop or need to run engine under these condition.

 

[johnalison]

Adding a panel or panels will certainly help. I have a 36w panel which gives useful results but doesn't keep with the fridge, but the greatest improvement I made was adding an extra battery, increasing my bank by 50%.

 

[ithet]

Adding a panel or panels will certainly help. I have a 36w panel which gives useful results but doesn't keep with the fridge, but the greatest improvement I made was adding an extra battery, increasing my bank by 50%.

I have 3 X 80Ah on domestic bank.

 

[JumbleDuck]

I am looking at fitting semi flexible solar onto the hatch garage as I have nowhere else to mount panels. I can get a max 80w panel that just fits the total area available. However, I could alternatively fit two narrow 30w panels side by side lengthwise in the same area. As the boom will give partial shading I want to know if the option of the two lower output panels wired in parallel (or with separate controllers if necessary) will provide a better solution (i.e. higher average output). What is the experts opinion?

I played around with my similar setup, and concluded that shade isn't a huge problem. It only really matters when the umbra (A on this diagram)

completely covers a whole cell. That's enough to kill output. However, that happens very rarely. When the umbra covers only part of a cell, or when the penumbra covers all of it, you get a reduction in output, but the rest of the cells keep things moving along. Also, sailing boats, and therefore shadows, move around all the time, so even if the umbra kills things, it's rarely for any length of time. Even at a pontoon, the sun moves and the shadow has only a temporary effect.

In other words ,,, don't worry about it, and just fit the biggest output you can.

 

[MikeBz]

It depends whether your panels have bypass diodes. If they are cheap ones then this is unlikely, in which case a small amount of shade has a drastic effect on the output. For this reason I fitted 2 smaller panels so that at least one of them is unlikely to be shaded - for me this was a big improvement over a single bigger central panel.

 

[Graham376]

We have 4 x 43w Kyocera (all in parallel) on the gantry plus a 25w semi flexible on the aft cabin coachroof. All suffer shading at different times, the coachroof one from the bimini and the gantry ones from the Aerogen. As we swing on the mooring and the Aerogen shadow moves onto one or two gantry panels there's a noticeable drop in charge but, we're still charging from the others, same applies when bimini shades the small one.

I'm planning on removing the Aerogen and replacing the Kyoceras with 2 x 150w panels which I will try in series and parallel to see what the difference in charge is. The small 25w panel will have to be through separate controller if I series the other two.

 

[Boathook]

I fitted a spectralite 50 which can be totally shaded at times. It still produces the volts but I suspect that current is well down when this happens. I'm more than likely going to fit another smaller one in parallel next year to boost output.